1. Field of the Invention
The invention relates to a method for operating a programmable washing machine comprising a laundry drum arranged rotatably inside a soap-solution container, which can be moved program-dependently with different speed profiles in both directions of rotation and comprising a real-time clock by means of which the user himself can determine the beginning or end of the washing process.
Appliances are supplied by a number of washing manufacturers in which an anti-crease function is fixedly installed as a section incorporated after the final spin. In these known appliances the anti-crease program section or the duration and sequence is the same and fixedly predetermined for all types of laundry and all loads. The user of the washing machine merely has the possibility for switching off the anti-crease system. Further interventions are not provided.
In washing machines during spinning at the high speeds normal today, it regularly occurs that a ring of laundry forms on the inner wall of the drum which frequently does not become detached even after the drum has stopped. This results in increased creasing and makes it difficult to unload the drum. The laundry ring has a very disadvantageous effect when a drier is integrated in the automatic washing machine. An non-detached laundry ring hinders uniform and rapid drying of the washing. In order to counteract this, an anti-crease operation is incorporated after the spinning in many washing machines. In this case, the drum is moved for a short time at a speed below the feed speed in several intervals in the direction opposite to the direction of rotation during spinning. In many cases, this is sufficient to detach the laundry from the drum and disentangle it.
2. Description of Related Art
Such a reversal of the direction of rotation to disentangle the washing in the drum is known from DE 41 15 776 A1 as an intermediate step during rinsing and spinning wherein here the emphasis is not on the anti-crease system but the redistribution of the washing in the drum for better rinsing and final rinsing of the individual items of laundry. DE 198 31 617 A1 describes a method for determining the quantity of washing in a drum in which a plurality of laundry disentanglement steps are provided for error correction.
The methods described with the fixedly predetermined parameters for speed, acceleration and braking speed are not optimal with reference to effective anti-crease system. With the known methods or process steps the anti-crease function cannot be adapted to the different conditions such as load and textile properties of the washing. The methods provide no satisfactory certainty that the laundry ring is actually detached. This is especially problematical at speeds above 1400 min−1 at which the laundry ring adheres tightly to the inner wall of the drum and is inherently relatively stable.
DE 199 47 307 C1 describes a method in which the final spin is followed by a program section in which the detachment of the laundry ring from the inner wall of the drum is monitored by measurement technology. For this purpose the mechanical vibrations of the soap-solution container as a result of falling washing are recorded. This is accomplished by evaluating the dynamic signal fraction of a position or force sensor or by evaluating the signals of an acceleration sensor. In order to avoid misinterpretations of the measurement data for very small quantities of laundry, the weighting value which was determined during the washing process or input by the user, is incorporated during the internal evaluation by the microprocessor control system. After identifying a laundry ring, an attempt is made to detach the laundry ring by controlling the drum drive with short and strong accelerating or braking pulses. The success of this measure is then checked by re-evaluation of the sensor signal.
The method described also provides no possibility for intervening in the automatically running program and individually manipulating according to the wishes and experience of the user. The success of the method described in relation to the detachment of a laundry ring adhering to the inner wall of the drum depends only on the sensitivity and accuracy of the sensors, which is problematical with very small amounts of laundry or very light laundry.